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In the news: scientific expert evidence

11 Apr 2013

Hugh Selby is an Associate Professor in the Law Faculty of the Australian National University and co-editor of Expert Evidence, a unique and well respected publication offering comprehensive coverage of over 75 expert witness fields. Below, Hugh draws on years of expert evidence experience to give us his take on the latest news regarding scientific evidence:

Popular wisdom is that it is advances in DNA science that exonerate wrongly convicted prisoners. Actually it is steady advances across the range of forensic sciences and dogged determination by 'innocence project' staff that reveal past error. A recent, well publicised example is the release in Texas of alleged hotel arsonist Mr Louis Taylor. The team that re-examined the 'expert' evidence used to convict him found that it was faulty. The pity for Mr Taylor is that it took 42 years to uncover that.

An ever present danger with experts and their evidence is overstating the strength of the result. Lay people, meaning anyone outside the particular expert field, must rely upon the expert's opinion because those lay people have no way of knowing that the science is not good enough.

Mr Taylor's recent appeal, like so many other contested conviction cases, could not prove his innocence (though he has always asserted that), but it could demonstrate that the science used to convict him was unreliable and misled the court.

The approach to the assessment of forensic evidence is improving because of more and better training, better field and laboratory equipment and methods, and a heightening awareness that forensic scientists must avoid any tendency to pre-judge the evidence. It is, as humans, so easy to look for the evidence and the interpretation of the evidence that supports, 'We think he's guilty", when the only correct approach is to evaluate each piece of evidence against the two hypotheses: that he is guilty, that someone else is guilty.

Investigators, prosecutors, defence lawyers, and judges sitting alone will find very useful information about experts and their evidence in Expert Evidence. To avoid the awfulness of Mr Taylor's fate, not to mention those wrongly convicted who have died before the errors have been discovered, proper preparation is not too much to ask is it?